镁合金铸轧过程中表面点状偏析形成机制

Formation of Surface Bleeding Segregations during Twin-Roll Casting of Magnesium Alloys

摘要:

采用金相检测与扫描电镜观察等方法，分析了镁合金铸轧板坯表面点状偏析的微观组织与微区成分，结果表明：表面点状偏析由富含Al、Zn溶质元素的金属间化合物组成，而Mn元素在偏析区域内含量与基体相同；偏析区域内组织主要为细小等轴晶粒。采用快速停车的方式获取镁合金铸轧板坯急停试样，分析镁合金铸轧板坯表面点状偏析的形成过程；在此基础上，分析了溶质Al、Zn和Mn元素在偏析区域内分布特征

Abstract:

Microstructure and micro-area chemical composition of surface bleeding segregations of magnesium alloy strips processed via twin-roll casting were investigated by OM, SEM and WDS. The results indicate that surface bleeds are composed of solute-rich intermetalics of Al and Zn element, the percentage composition of Mn element in surface bleeds is similar to that of the matrix alloy. The structure of surface bleeds changes into equiaxed grain with fine grain size. Stop-samples were achieved by abruptly interrupting casting for analyzing the solidification and deformation characters in the set-back of magnesium alloys strips, and the formation mechanism of surface bleeds were discussed. Furthermore, the characteristics of solute elements distribution in surface bleedings including Al, Zn and Mn elements were discussed